Study of genetic diseases with neoplastic manifestations and detailed investigation of families with high risk of cancer may help detect environmental and genetic influences in carcinogenesis, especially when appropriate laboratory assays are used. Clinical recognition of accessory nipples in two patients with kidney cancer led to a case survey that found a 50-fold risk of accessory nipples in renal cell carcinoma patients. In vitro radiation sensitivity was unusually high in a family with acute myelogenous leukemia and a radiogenic rectal carcinoma, and unusually low in one with diverse malignancies. A family with Waldenstrom's macroglobulinemia had a broad clinical and laboratory spectrum of immune defects. Genetic consultations led to devising a generalized statistical method for designing family studies and to recognition of a new X-linked immunodeficiency syndrome with growth hormone deficiency. Guest lectures, literature reviews, and committee activities were done to stimulate similar research worldwide.